This statement in 1906 seems to be the earliest attempt at a quantitative definition of deficiency. As I discovered it after the present monograph was practically completed, it furnishes evidence of the natural tendency of attempts at more exact definition to take the percentage form. Footnote 8: C. Macfie Campbell. The Sub-Normal Child—A Study of the Children in a Baltimore School District. Mental Hygiene, 1917, I, 96-147. Footnote 9: Italics mine. Footnote 10: The report of the Massachusetts Commission on Mental Diseases (Vol. I, p. 198) shows that social agencies systematically using mental tests reported 19.2% as mental cases, while those using examinations only for obvious cases reported 1.3%. CHAPTER V. ADAPTING THE PERCENTAGE DEFINITION TO THE BINET SCALE Sufficiently large random groups have not been tested with any development scale to make the determination of the borderline on the scale more than tentative. Such borderlines must be looked upon as temporary descriptions to be used in aiding diagnosis until more data are available. Nevertheless, the percentage method of procedure seems to be an improvement over other plans of stating the borderline. So far as the Binet 1908 scale is concerned, when we supplement Goddard's results with 1500 school children by the data for the lower limits of a random group of 653 15-year-olds which we tested, the limits on the scale for passable intellects defined by the percentage method will be found, I believe, not only more conservative, but more reliable than those in current use. Moreover the intended meaning of such borders becomes clear. A. THE BORDER REGION FOR THE MATURE. (a) INDICATION FROM A RANDOM GROUP. The passing limit for adults is unquestionably much more important than that for children since any child who once passes this limit is assured, generally speaking, of social fitness so far as intellect is concerned. He has attained a position intellectually which is sufficiently good to enable him to get along without social assistance unless he is especially deficient in will. This borderline for the mature has been so thoroughly neglected that in none of the common published forms of the Binet scale, except the new Stanford Scale, is there an attempt to define it. This seems almost incredible in view of the general use of the Binet method in diagnosing feeble-mindedness. To be sure, there are discussions of this upper limit, as we shall see, but they have usually not been embodied in the actual directions accompanying the scales which get into the hands of amateurs. Most of these directions content themselves with describing borderlines for children with no caution about the final lower limit for social survival.